In this post we are going to look at a feature called "Try Next Closest Site" which is enabled on Windows Vista upwards clients via Group Policy.

In Windows 2000/XP/2003 when all domain controllers in an Active Directory site fail, there is a chance workstations may failover to another Active Directory site at a higher cost then the most preferable one as defined in Active Directory Sites and Services. Changes have been made to the DC Locator algorithm starting from Windows Vista/2008 Server onwards which improves the DC Locator algorithm to ensure workstations always communicate with the next closest Active Directory site as defined in Sites and Services.

I strongly recommend this setting always be configured if your workstations are Windows Vista or higher. To enable this setting perform the following.

Note: With "Try Next Closest Site" it will never try a remote site which contains a read only domain controller as read only domain controllers generally only store passwords for the users at the specific remote site for security reasons.